Morphosyntactic Convergence vs. Pragmatic Drift: A Contrastive Evaluation of Contact-Induced Grammaticalization Pathways in Heritage and Immigrant Bilingual Varieties

Abstract

This study investigates competing theoretical frameworks for explaining grammatical restructuring in heritage and immigrant bilingual varieties, with particular focus on contact-induced grammaticalization as a driver of morphosyntactic convergence and pragmatic drift. Drawing on a cross-linguistic corpus of spontaneous speech and elicited narratives from 214 bilingual speakers across four typologically distinct language pairings, we apply variationist sociolinguistic analysis alongside Optimality-Theoretic constraint ranking to evaluate the predictive power of each framework. Results indicate that morphosyntactic convergence models account more reliably for nominal and verbal paradigm erosion, whereas pragmatic drift frameworks better capture discourse-level restructuring in evidentiality and aspect marking. The findings carry significant implications for theories of language attrition, bilingual grammars, and heritage language pedagogy, and challenge monolithic accounts of contact-induced change.